Automatic transmission



Aug. 7, 1945. r.- B. T YLER AUTOMATIC TRANSMISSION Filed Sept. 11, 1939'11 Sheets-Sheet l Aug. 7, 1945. f T. B, TYLER 2,381,786

AUTOMATIC TRANSMISION Filed Sep tfll, 1959 ll Sheets-Sheet 2 FIG.2A.

Aug. 7, 1945 TYLER 2,381,786

AUTOMATIC TRANSMI S SION Filed Sept. 11, 1939 r 11 Sheets-Sheet 5 awuemmg- 7, 1945. v B. TYLER 7 2,381,786

AUTOMATIC TRANSMISSION Filed Sept. 11, 1959 i 11 Sheets-Sheet 4 FFlG.2.C.

WITH! 1945- T. B. TYLER 2,381,786

AUTOMATI C TRANSMI S SION Filed Sept. 11, 1939 ll Sheets-Sheet 5 Aug. 7,1945. T. B. TYLER AUTOMATIC TRANSMISSION 11 Sheets-Sheet 6 7, 1945- -T.B. TYLER AUTOMATIC TRANSMISSION Filed Sept. 11. 1959 ll Sheets-Sheet 7lznzamrq 7 III/II l I Aug. 7, 1945 TYLER 2,381,786

AUTOMATIC TRANSMISSION Filed Sept. 11, 1939 11 Sheets-Sheet FIG.I4'.

FIG.I3.

AUTOMATIC TRANSMISSION Filed Sept. 11, 19 59 7 1i Sheets-Sheet l0 Ill QG Ill U Q NEUTRAL Aug. 7, 1945. T. B. TYLER 2,381,786

AUTOMATIC TRANSMISSION Filed Sept. 11, 1939- ll Sheets-Sheei 11INVENTOR.

ArroRzvsy v. .3 & N

Patented Aug. 7, 1945 AUTOMATIC TRANSMISSION Tracy Brooks Tyler,Chicago, Ill., assignor to The Monopower Corporation, Detroit, Mich, acorporation of Michigan Application September 11, 1939, Serial No.294,256

22 Claims.

This application constitutes a continuation in part of my copendingapplication Serial No. 216,-

983, filed July 1, 1938, for Automatic transmission,

1 now Patent No. 2,204,919.

The present invention concerns itself with clutch constructions of thetype controllable automatically in response to speed changes of one ofthe elements which it serves to couple. An important object of theinvention is to provide such an automatic clutch which responds, afterthe fashion of a conventional centrifugal clutch, to the speed of thedriving shaft, but in which the force applicable to efiect engagement ofthe clutch, while controlled by, is not dependent upon the forcedeveloped by the centrifugal weights.

A further object is to provide such an automatic clutch operable byfluid pressure, the fluid pressure in turn being controlled by acentrifugal mass or masses, which may if desired be located at a pointremote from the clutch controlled thereby.

A further object is to provide such an automatic clutch mechanism whichmay be easily overcntrolled by the operator, in such manner as not onlyto permit disengagement of the clutch at any time, but to enablecontinuous variation of its operating characteristics, such as the speedto which it engages and disengages, by merely operating a pedal orlever.

7 Still another object is to provide such an automatic, centrifugallycontrolled, fluid-operable clutch construction whose operation, bothwhen automatically induced and when actuated by the overcontrollingmechanism, is virtually unaffected by the changes of viscosity of theactuating fluid.

Still another object is to provide such a clutch construction which isengageable and disengageable automatically in response to speed changesof the driving shaft, but which incorporates supplementary means inresponse to the speed of the driven shaft for locking the clutch inengagement when the driven shaft is turning at higher than apredetermined rate.

Still another object is to provide in such a fluid operable clutchmechanism improved means for offsetting unwanted effects of centrifugalforce upon the operating fluid.

Other objects and advantages will be apparent from the followingdescription wherein reference is made to the accompanying drawingsillustrating preferred embodiments of my invention, and wherein similarreference numerals designate similar parts throughout the several views.

In the drawings:

Figure 1 is a composite view, partly in central longitudinal section andpartly in side elevation, with the housing broken away, showing a preierred form of the invention.

Figures 2-A, 2B and 2C are views showing respectively the left-hand,central and right hand portions of the transmission as shown in Figure1, but upon an enlarged scale.

Figures 3, 4 and 5 are cross-sectional views tak en substantially on thelines 33, 44 and 5-5,

respectively, and looking in th direction of the arrows.

Figure 3A is a detailed cross section of one of the valve bodies shownin Figure 3.

Figure 6 is a sectional view of the automatic valve actuating plunger.

Figure 7 is a similar sectional detail of one of the valves.

Figure 7-A is an enlarged detail of such valve, partly in section andpartly in elevation.

Figure 8 is a sectional detail taken substantially on the line 8-8 ofFigure 2-C, and looking in the direction of the arrows.

Figure 9 is a sectional detail taken substantially on the line 9-9 ofFigure 2--B, and looking in the direction of the arrows.

Figure 10 is a detail perspective view of one of the elements of thedisengaging mechanism of an overrunning clutch.

Figure 11 is a diagrammatic sectional view of the cooperative automaticvalve mechanism and manually operable over-control valve, showing thevalves in positions they normally occupy when the vehicle is at rest.

Figures 12, l3, 14, 15 and 16 are similar schematic views showingpositions assumed by the valve during operation of the transmission.

Figure 17 is a side view of the manually operable overcontrol valve.

Figure 18 is a detailed cross sectional view taken substantially on theline l8-l8 of Figure 17, and looking in the direction of the arrows. IFigure 19 is a vertical section similar to Figure 2, and showing asomewhat modified clutch actuating mechanism.

Figure 20 is a cross section thereof corresponding to Figure 3, takensubstantially on the line 20-20 of Figure 19, and looking in thedirection of the arrows.

Figure his a sectional detail, upon a larg r scale, of the manualcontrol valv for the clutch actuating mechanism, and adjacent parts.

As best shown in Figure 1, the transmission mechanism is housed in acasing H2 forming a rearward extension of a clutch housing I ID, with inwhich is arranged a main clutch drivable by a flywheel I from an engineor other suitable source of power. Although the illustrated main clutch,generally designated A, is of a novel design, operating upon principlesdisclosed in my copending application Serial No. 206,955, filed May 9,1938, the use of a clutch of this type is not essential.

General arrangement and operation of torquetransmitting parts Beforedescribing the detailed structural features of the mechanism, and itscontrolling means, the general arrangement of the gears and clutches,and the manner in which they function to transmit the drive at differentratios, will be set forth. This will afford a general understanding ofthe entire construction which, it is believed, will be helpful inunderstanding the signiflcance of the individual features of theapparatus.

The main clutch, generally designated A, is of the friction type and iscentrifugally controlled in response to the speed of the driving elementI0', which is shown as a flywheel rotatable by an engine (unshown). Whenthe speed of the flywheel rises to a predetermined rate, this clutchengages (gradually by means presently to be described) to connect thetransmission shaft 20 to the flywheel and engine. Additional fluidoperable friction disc clutches, generally designated B, C, D, E and F,are grouped concentrically along the transmission shaft 20 and drivenshaft I00. The clutches B, C, D and E are arranged generally in thecentral portion of the casing, while the gearing, comprising two sets ofplanetary gears, each surrounded by an internally toothed ring gear withwhich the planet gears mesh, is located at the rear, or right end of theassembly as shown in the drawings, one of such two gear assemblies beingdisposed upon each side of the clutch F.

Referring to Figure 1, and to Figures 2-A, 2B, and 2-0, which areadapted to be considered as juxtaposed in the order named to afford anenlarged view, a first speed (high torque) drive is provided when onlyclutches A, C and E are engaged, and may be traced from the flywheel ordriving element I0 through locked out overrunning clutch 30 (which islocked out by engagement of clutch C, although this is not essential) toa sleeve 40, which, in the form of a drum, encloses clutches D and E.Drum 40 drives ring gear 50 of the first planetary gear assembly, andthereby tends to roll the planetary gear 60 upon the sun gear I0. Thesun gear I0 is in the form of a sleeve freely rotatable upon the drivenshaft I00 and toothed at both ends, forming, as shown, the sun gear forboth planetary systems. The cage or spider 6| by which planet gears 60are carried is directly connected to the driven shaft throughoverrunning clutch I30, plate I I6, drum I I4 and hub I I5, the lattersplined to the driven shaft I00. The engagement of clutch E alsoprovides direct connection between the gear cage GI and drum Ill. Due tothe resistance of the load. planet gears 50 tend also to rotate sun gear.10 in the reverse direction, and such force tends to rotate planetgears 00 of the other planetary set about their individual axes, sincethe cage 0| by which planet gears 00 are carried is held againstrotation by the overrunning clutch III. Rotation of planet gears 00tends to drive the internal toothed ring gear 00 meshing therewith inthe forward direction,

gear 00 being also directly keyed to the driven shaft. Due to the loadthus transmitted back through gears .90 and '80 to sun gear I0, thelatter is allowed to rotate at a reduced rate in the opposite directionas the planetary gears 60 roll thereover at a reduced speed. Thecombined action of the two gear assemblies thus provides a reduced orfirst speed drive.

In forward speeds, clutches C and E merely act to prevent overrunning ofthe overrunning clutches 30 and I30, whenever they are being used in theline of drive. It is not necessary that clutches C and E be engaged asdescribed in the first speed condition, however, as the vehicle willcoast anyway because of the presence of overrunning clutch III.

When the second speed drive is in operation, only clutches A, C, E andF, are engaged. The drive is then, as in first speed, throughoverrunning clutch 30, sleeve 40 and gears 50 and B0 to sun gear I0, butclutch F rigidly holds the sun gear against rotation with respect to thecasing, so that the planetary gears 60 roll freely on the sun gear andthe drive is transmitted to shaft I00 only through the cage SI of theseplanetary gears, and through drum housing II4 and hub Hi to the drivenshaft. overrunning clutch III allows planetary gears 80 to roll freelyupon sun ear I0.

A third speed drive constituting a direct drive between the flywheel anddriven shaft is effective when onlyv clutches A, B, E and F are engaged.The drive is then from shaft 20 through clutch B to its hub II'l, whichis journaled for free rotation upon shaft 20 and connected through a webII6 to drum IIB, which encircles both drums 40 and Ill and enclosesclutches B, C, E and F. Drum H8 is connected by means of its oppositeend web II9 to the cage 6| of planet gears 60. Such cage, as previouslystated, is directly connected to the driven shaft through overrunninclutch I30. Since the sun gear 10 is still held stationary by engagementof clutch F, the cage 0| rotates at the speed of the driven shaft and adirect drive effect is secured. The ring gear 50 drives sleeve 40 in thesame direction at an increased rate of speed, such sleeve overrunning onoverrunning clutch 30. Clutch E prevents overrunning through overrunningclutch I30.

An over-drive fourth speed is provided when only clutches A, B, D and Fare engaged. The drive is through the same elements up to the planetgears 60. From these the drive is now transmitted to the ring gear 50,which drives'the driven shaft at an increased speed ratio through clutchD and its hub I I5 which, as stated, is keyed to the driven shaft.Clutch E then being released, overrunning clutch I30 overruns, and sungear I0 being held stationary, the drive from the planet gears 60rotates the ring gear 50 at the proper speed for over-drive.

For reverse drive, only clutches A, B and C are engaged, while by meanspresently to be described, the overrunning clutch I30 is completelyfreed at this time, allowing independent rotation of its inner and outerraces. Simultaneous engagement of clutches B and C is equivalent tolocking together planet gears 60 and ring gear 50, since clutch B locksthe driving shaft to the cage of planet gears 60 through its hub I I1and drum II8, while clutch C locks the driving shaft .to the ring gear50 through drum 40. In this condition, the sun gear I0 becomes unitarywith the planet set 50-40 and rotates planet gears 80 in reversedirection. Since, as stated, overrunning clutch III, during reverse Mainclutch construction and operation Referring to Figure 2--A, the facings35 on clutch disc 38 and pressure plate I34 of the main clutch will beseen to be enclosed within a cover plate I6 bolted at its periphery tothe flywheel. The pressure plate is suspended upon radially disposedflat spring elements I42 secured at their inner ends to the cover plateH8 and at their outer ends to the pressure plate, these springs urgingthe pressure plate toward released position and holding it againstradial movement with relation to the cover. When the pressure plate isforced toward the flywheel, to clamp the clutch disc 36, the lattertransmits the drive to'the hub 2I by which it is carried, throughcushion springs 32. The hub is keyed to the shaft 20.

To apply pressure to the pressure plate to engage the clutch in themanner described, pressure fluid is admitted, in a manner which willpresently be described, to a chamber 33 behind a piston I3I in acylinder I32, all of these parts being disposed concentrically with theaxis of the assembly, as are the other parts to be described. The pistonabuts a slidable sleeve I33, which in turn abuts at I35 the pressureplate I34, projecting into engagement therewith through openings(undesignated) in the cover plate I8. Movement of the piston due topressure in the chamber 33 may thus move the pressure plate to engagethe clutch. The reaction of the force developed is taken against ashoulder I35 on a sleeve I31, which sleeve is fixed by means of a snapring I38 to the cover plate I6 of the main clutch. The pressuretherefore exerts no thrust against the flywheel bearing, or thetransmission bearing, as the pull comes against the snap ring I38 andthe thrust against the clutch pressure plate at its abutment I35(through which the pressure plate is actuated). This will be seen to tiethe clutch actuating cylinder to the clutch and its cover as a unit,although the actuating cylinder will be seen to be enclosed within thetransmission housing and separated from the main clutch by a coverportion 33 secured to the casing assembly IIO-II2.

The sleeve I31 is also splined to the clutch cover plate I8 andaccordingly it, together with the cylinder I32 and all its componentparts, revolved with the flywheel.

Upon the opposite side of piston I3I is a chamber I40 formed by a plateI4I sealed at its inner and outer peripheries. Fluid seeping past thepiston keeps chamber I40 filled at all times. The purpose of this is tobalance off centrifugally the effect of the forces so generated by thefluid in the chamber 33 when the cylinder I32 is revolved at high speedby the engine, without the engagement of the main clutch being desired.Without this provision centrifugal pressure generated in chamber 33would urge the piston I3I to the left to apply pressure to plate I34without control. When fluid pressure is shut off from chamber 33, it isshunted to the chamber I40 through a conduit 43 and port 44. This, andthe peripheral positioning of the vents of chamber 33, provides forinstant release of the clutch, even though the fluid may be thickened bylow temperatures in cold weather.

In Figure 3 is shown the means by which the main clutch is centrifugallyoperated in conjunction with mechanical fluid pressure.

At all times when the engine is running, fluid pressure is supplied, bymeans presently to be described, to a conduit I45. The entire unit shownon the drawings, being carried by the cylinder body I32 within thecompartment defined by partitions 39, I33, revolves with the flywheel.Flyweights 48 pivoted as at I48 upon the casing I32 are urged outwardlyby centrifugal force and inwardly by fluid pressure, assisted by springI49.

The parts are shown in clutch released position, in which a slidingvalve I48 is in such position that the fluid is admitted only to valvechamber I41, and from it into conduit 43, which as shown in Figure 2-A,is connected to the clutch releasing chamber I40, the result being thepositive maintenance of the clutch in released position.

When the assembly revolves at sufficiently high speed so that forces ofthe centrifugal weights 48 overcome the tension of spring I49, the valveI46 begins to move toward the right until chamber I50 comes partiallyinto registry with the conduit I45. Through an axial bore I52 in thevalve, the pressure fluid is conducted from chamber I50 to chamber I5I.During this movement the pressure fluid escapes from conduit 43 throughan escape port I54, thereby venting clutch chamber I40. The pressurefluid attempts to escape from chamber I5I through a second escape portI55, and if the speed of rotation is not great enough to generatesuificient centrifugal force from the weights 48, the fluid does escapewithout building up any pressure in the chamber I5I. If the rotationalspeed be gradually increased from this point, the valve in conjunctionwith outlet I55 will act in the manner of a spring-urged relief valve,and will attempt to close off port I55 with increasing force, therebygradually building up the pressure in the chamber I5I, and hence in thepiston chamber 33, which is connected thereto by a passage I56. Hence inthe chamber 33 the fluid pressure corresponds to the centrifugal force,at the different speeds, until a predetermined maximum pressure has beenobtained. Such predetermined maximum is delimited by a relief valveprovided in another part of the system and presently to be described.After a predetermined maximum speed of rotation has been attained, theflyweights 48 are stopped by engagement with lugs I51, port I55 beingthen fully closed.

Another valve I58, also controlled by the flyweights and relatedelements is arranged to maintain engagement of the clutch A whenever thetransmission is in second speed or higher. This valve also causesengagement of the main clutch in such manner as to allow starting theengine of the motor vehicle by towing. Fluid-induced operation of thisvalve is provided through a conduit I59, which communicates with thefiuidpressure supply source from chamber 205 (Figs. 5 and 11-16inclusive) through ports 2), 221, 228, when the main control valve 20Iof the transmission is shifted to second speed position or higher. Theoperation of the control valve will presently be described. When fluidpressure is thus introduced into chamber I60, valve I58 is moved all theway to the left, which moves the flyweights fully outwardly and valveI48 all the way to the right. A port IBI also communicates with thevalve chamber I60 when valve I58 is at the left end of its movement.Port I6! communicates with clutch actuating chamber 33, although portI6I is not opened to provide such communication until after escape portI55 of valve I46 has been fully closed. This arrangement will be seen tomaintain the main clutch A in engagement whenever the transmission is insecond speed ratio or higher.

Fluid pumping system The transmission is equipped with two fluid pumps,62 and 63. The pump 62, near the front end of the transmission, isdriven only by the engine, its rotor I62 being splined to the sleeveI31. The rear pump 63 has its rotor I63 splined to the hub of thegovenor 15 (presently to be described), which is splined to the drivenshaft I00. As shown in Figure 1 both pumps may draw their supply througha common screen I09, from the sump of casing H2.

The output of the front pump is connected to the clutch control valveI46 shown in Figure 3 through passage 220, best shown in Figure 5,manifold passage 22I (Fig. 2A), and bore I45. Before entering passage220 the fluid passes through a check valve 2 I 3, and the supply is alsoconnected to a part of a manually operable valve 230 (Figs. 7 and 'l-A).The purpose of these valves will presently appear. Fluid from the frontpump is also conducted to the main control valve system, consisting ofvalves MI, 204, through a passage 2I9.

From the output of rear fluid pressure pump 63 (Fig. 2-C), a conduitbore I10 conducts fluid to a chamber Ill, and thence through ports I12,I13 to valve chambers I14 and I15 (Fig. 4). The action of the valvesystem shown in the last mentioned figure will also presently appear.

General features of transmission clutches In view of the fact thattransmission clutches B, C, D and E and their component fluid pressurechambers are, at various times, revolved at relatively high speeds, itis necessary that the effect of the fluid in the pressure chambers becounteracted at all times, while the drums are revolving. This isachieved in a novel manner which involves moving the external drums orcylinders axially to engage and disengage the clutches, rath'er thanmoving piston plates or the like with relation to the cylinders. Thepiston plate element of each clutch is fixed to the driving hub orsupporting shaft, while the surrounding cylinder portion is slidablysplined to the hub sleeve or shaft, as indicated at I64, by means ofplates, as I65.

For the clutches B and C, three fluid pressure chambers I66, I61, andI68 are provided. Fluid is admitted to the central chamber I61 under jut enough pressure to keep it full, while fluid under full clutchoperating pressure may be admitted to either of the chambers I66, I68.It will be seen that such full fluid pressure, when admitted to chamberI66, tends to move the drum 66 of clutch B to the right to apply thatclutch, while likewise admission of such full fluid pressure to chamberI68 tends to apply clutch C by moving its drumshaped casing 68 to theleft as viewed in the fig- .ures. When both clutches B and C aredisengaged androtating at high speed, the centrifugal force of any fluidin chambers I66 and I68 which might tend to cause their engagement isoffset by a similar force in the chamber I 61, which tends to spread thecylinders 66, 68 apart toward disengaged position. Chamber I61 isenclosed by a sleeve 61 secured to one of the cylinders as 66, and insubstantially sealed slidable engagement with the other cylinder 68,which carries packing means 69 to cooperate with sleeve 61.

In addition to the centrifugal balance provided by central chamber I61,a coiled retractor spring I69 normally maintains the clutches in theirreleased positions. When fluid under mechanical operating pressure isadmitted to either one or both of the chambers I66, I68, the onlydeduction from the total pressure will be that of spring I69, since thecentrifugal forces are balanced and independent of the mechanicalpressure under all conditions.

Since the clutches D and E are never engaged simultaneously, no extrabalancing chamber is necessary. When fluid pressure enters one of thepressure chambers, as chamber ,11 of clutch D, it is ejected from theother pressure chamber, as chamber 18 of clutch E, and vice versa.

The cylinders of these clutches move as a unit, and from the drumassembly II4. When this assembly is moved in one direction it appliesone clutch and releases the other and vice versa, so that the fluidpressure which engages one clutch positively disengages the other,insuring instant release whenever the other is engaged.

Clutch F requires no centrifugal balancing since only its friction plate83 rotates relatively to the housing, its drum 89 being bolted directlyto a web II3 which in turn is fixed to the casing.

Governor and valve means for automatically controlled actuation oftransmission clutches Actuation of the transmission clutches iscontrolled automatically through the cooperative action of a governor,best shown in Figure 4, and automatically regulated valve means shown inthat view and in Figures 5, 6 and 7.

From the output of rear fluid pressure pump 63 (Figure 2-0) a conduitbore I10 conducts fluid to a chamber HI, and thence through ports I12,I13 to valve chambers I14 and I15 (Figure 4).

The entire assembly shown in Figure 4 rotates with the driven shaft I00,and at low speeds its flyweights I16 remain in their indrawn positionsin which they are shown. The pressure fluid from port I12 then passesfreely out of the valve chamber I14 through an escape port I11.

A conduit (not shown) connects the distribution chamber "I with inletport I18 of a piston plunger I19 which actuates the main automatic valve20I, being mechanically connected thereto by a rod 202 which connectstheir projecting head portions. The plunger and valve lie parallel andadjacent to one another at a point near the front of the transmission,the plunger being shown separately in Figure 6.

Upon increase of the rotational speed of the governor, the tension ofspring I is overcome sufficiently so that the flyweights, which arearticulated as by links 11 for simultaneous movement, move outwardlyuntil thelug IBI of the right hand flyweight arm, as shown in Figure 4,engages and is stopped by the end of valve plunger I82. The port I11 issimultaneously closed by a similar lug I 8IA carried by the left handflyweight arm, which moves valve I 91 to the right sufficiently for thispurpose. An initial predetermined fluid pressure is thereby created,which is delimited by a spring held relief valve I83 which the fluid,entering through port I13, must depress against its spring I84 to escapethrough the port I85. Assuming some predetermined fluid pressure, suchas, for example, 20 pounds to the square inch, is thus created in thesystem, the spring I86 of the plunger I19 is thereby compressed to apoint where it equals 20 pounds per square inch, and at this point arecess I81 in the plunger becomes aligned with spring pressed detentballs I88. The detent balls are provided to properly register theplunger at this point, even though some variation from the predeterminedfiuid pressure might be required to maintain the exact position.

With further increase in the rotational speed of the governor, andcorrespondingly further outward movement of the flyweights, the springI89 of the valve plunger I92 is compressed, and the spring I89 furthercompressed until the outer lugs I99 of the flyweight arms come incontact with and are stopped by the spring projected plungers I9I. Inthis condition the chamber of valve I83 has been closed off, by thisfurther movement of the valve plunger I82, and the pressure in the.system is increased to the pressure required for the fluid entering thevalve assembly through port I12 to move the relief valve I92 against theresistance of its heavier spring I93 and escape through the escape portI94 thereof. It may be assumed that this valve establishes a higherpressure, such for example, as 49 pounds to the square inch. I

With this amount of pressure in the system, the spring I88 of the valveoperating plunger I19 is further compressed to the point where itstension is equal to 40 pounds per square inch, at which point the recessI95 is arranged to come into registry with the spring detent balls I89.

At a still higher governor speed, the springs I98 of the plunger I9I areovercome, and springs I89 and I89 are also further compressed, whereuponthe chamber of the relief 'valve I92 becomes closed by the valve plungerI91, thereby closing the last escape port and bringing the pressurevalve actuating system up to the maximum pressure, which may bedetermined by a main relief valve (not shown) connected to the rearpump. Assuming this to create some such increased pressure as forexample 60 pounds to the square inch, the spring I86 is therebycompressed until the shoulder I98 of the plunger strikes a shoulder I99provided by the top of the spring well. It will be seen that the plungerI19 is in this manner moved to four different positions. When theflyweights of the governor have completed their outward movements in theorder described, they strike and are stopped by the rim of the governorhousing. This relieves the mechanism from strains due to extracentrifugal force. a

The valve actuating plunger I19 is connected to the automatic controlvalve 29I by a stem or rod 292 attached toa collar'293 carried by theprojecting end of the plunger. Movement of the plunger is therebytransferred to the valve 29! in accordance with the predetermined speedsof the vehicle.

Adjacent and in series with the automatic valve 29I is also arranged amanually shiftable valve plunger 294 arranged to overcontrol theautomatic speed-selective action of valve 29I, in a manner presently tobe described. Fluid at the pressure predetermined by the relief valve2I3 of the front pump and the similar relief valve (not shown) ofthe-rear pump is delivered to a recessed chamber 295 in automatic valve29I, fluid from the front pump entering through a passage 2I9 andpassing first through a channel 2I2 in the manual valve. Such valvechannel is so positioned as to close oil? escape of fluid from the rearpump when the manual valve is shifted to neutral position, although, ofcourse, with the transmission in neutral no fluid flows from the rearpump unless the vehicle is coasting or the driven shaft is otherwiseturned. Assuming for present purposes that the manual valve is in itshighest position, as shown in Figure 11, the progressive action of theautomatic valve 29I commences with the latter in its lowest position.

with the automatic valve in this position, fluidenters valve chamber 295from both pumps, as previously described, and can escape from thischamber only through passages 299E and 2I IC. Continuations (209e, 2||c).of these passages lead to the pressure chambers 18, I88 for theclutches E and C, respectively, through distributing means presently tobe described. As .previously stated, operation of the transmission infirst speed requires engagement of clutches A, C and E, so that firstspeed operation is then effected, as soon as main clutch A is engaged byits operating means previously described. It will be noted that themanual valve 294 IS also in series with the passages 299E, 2| IC, andarranged to enable interrupting the communication. With the manual valvein its raised ".lth position, however, valve channels 299K, 2IIX,therein provide straight through communication without interfering withoperation of the clutches in question.

It, with the manual valve remaining in the elevated position, theautomatic valve. 29I is raised, by its operating means previouslydescribed, to the position designated 2nd in Figure 11, communication isalso established with passage 2I9F, without interrupting communicationwith passages 299E, 2| IC. Passage 2IUF, through its continuation 2 I9!, is in communication with the pressure chamber of clutch F, when suchcommunication is not cut oif by the interposed manual valve, which isprovided with an appropriately positioned straight through" channel2I9X. With the automatic valve thus raised to 2nd position, clutches C,E and F- are engaged, and clutch A now becomes locked in engagement (ina manner presently to be described) as required for second speedoperation.

.Third speed becomes effective when valve 29I is lifted to the positiondesignated "3rd in Figure 11. The valve 29I will be seen to be sodesigned that this cuts off port 2I IC and establishes communicationwith passage 2963, whose continuation 29Gb communicates with pressurechamber of clutch B, through the interposed channel 206K of the manualvalve. Thus the clutches A, B, E and F may be concurrently engaged, asrequired for third speed operation.

Similarly, the next upward step of the automatic valve, induced by theactuating plunger I19, carries it to the 4th position, in which ports 2|IC and 299E are both out off, and communication is established with port298D. The continuation .portion 298d of the last mentioned port is incommunication with the pressure chamber 11 for actuation of clutch D,through the opening I96X in the manual valve 299. Thus it will be seenthat clutches A, B, D and F may be concurrently engaged, as required forfourth speed operation.

In normal automatic operation of the transmission, valve 294 remains upon the "4th position, and the automatic'valve 29I moves up and downthrough the several positions just described, under the influence of itsactuating means, which then controls the operation of the automaticclutches B, C, D, E, and F, which control the ratio changes in themanner also already described. The clutch A constitutes a simple andhighly eflicient automatic main clutch which engages smoothly as theengine speed is increased by opening the throttle to speed up the engineto a predetermined rate, but it will be apparent that the main clutchmight be operable manually or otherwise, rather than automatically.

The passages 208d, 203e, 2i lo, and 20Gb extend and are connectedindividually to the severalchambers 306, 30], 308, and 309 of adistributing manifold 55 (Figure 2-A) these channels being individuallyconnected by means of elongated recesses such as 3 I II in shaft 20, andby longitudinal holes (also undesignated) drilled in the shaft I 00, tothe pressure chambers of transmission clutches B. C. D and E.

Clutch F is not supplied through the manifold 55. Instead its passage 2Mis extended through the cap 34 of pump 62 and conducts the fluid througha port 228 to a recessed chamber 229 in the valve 230, which isseparately illustrated in Figure 7. From this chamber the fluid isconducted to clutch F through a port 2 and tube 242, the lattercommunicating, with a fltting 221 opening into the pressure chamber 33of this clutch.

The functioning of the valve 230 will presently be described. This valveand the other valves and related elements shown in Figures 4, 5 and 6are carried by and housed in a casing and support ll formed also tohouse the forward pump 62 and as a unit with the web I39.

In the passages leading to clutches B, C, D and F, ball check valves areinserted, as at 19 (Figure 2-0), which close toward the pressurechambers but allow a metered flow when closed, to feed the fluid tothese clutches at a predetermined rate when the valve is seated. Thiswill be seen to control the time required for engagement of theseclutches, making them engage smoothly and preventing Jerking of thevehicle, while the check valve opens fully in the opposite direction, toallow quick disengagement. The check valves for the other clutches (B, Cand- D) are not illustrated.

Before passing to the distributing chamber 205 through passages andorifices 2"), 2| 2, and 98, the-fluid from the front pump 52 isdelivered, under pressure, through a port 262 to a circular recesschamber 263 in the sleeve 264 surrounding valve 230 (Figures 7 and 7-A).Valve 23!! is situated in a bore directly forward of and closelyadJacent the vertically disposed axially aligned relief valves 2| 8 and2. From the chamber 263 the fluid passes to the chamber of the reliefvalve 2l3 through a connecting port 2i5. The position of connecting portor passage M5 is indicated in Figures 5 and 7-A. The pressure fluidurges the relief valve against the tension of a relief spring 2l6 farenough to escape from the side ports 2ll2|8 in the sleeve at apredetermined maximum pressure. The fluid delivered through port 2" isconducted through the conduit bore H9 and passage M2 in the valve 204 tothe chamber 205 of valve 2M. Fluid passing through port 2! is conductedthrough a bore 220 and connectin passages (unshown) to a recess 22l inthe pump body (Fig. 2-A) whence it is conducted to the conduit bore I45for operating main clutch A. The fluid is also conducted to the secondrelief valve 2 by a passage 222, which communicates with the passage 220and with a port 223. The relief valve 2 is also opposed by the oppositeend of the spring 2|6, and a predetermined pressure permits escape of apart of 2,ss1,7se

the fluid through a passage 224 and the remainder through a circularchamber 223 surrounding the'shaft (Figure 2-A) and a passage 223A, whichconnects with one of the conduit bores in the shaft I", from which it isdistributed to various points for lubrication and to fill the clutchpressure balancing chamber I" for clutches B and C.

Pressure fluid for maintaining engagement of the main clutch A after thevehicle has been shifted into second speed, and while it is in this andhigher speeds, is taken from the recessed chamber 228 in valve 233,which is supplied through the main control valve system 2M, 2 when thesevalves are so set as to call for operation of the transmission in secondor higher gear ratio. From chamber 223 the fluid passes through a port.2Iil and a connected passage 2" (Figures 5 and 'l-A), annular recess233 (Figure 2-A) and through the sleeve I31 to the conduit bore I53 andvalve I53 (Figure 3).

Manual ratio control means control the operation of the main clutchmanually whenever the operator so desires.

Another lever 235 also operable from outside the casing may be connectedby suitable linkage (unshown) or other means to a second manualcontrolling device, which may comprise, in automotive installations, aplunger or small lever on the instrument panel or steering column. Thisis arranged to provide manual control or manipulation of the speedchanges and of the neutral and reverse settings, and to enable theoperator to overcontrol the automatic action by moving the manual valve203.

Lever 235 is fixed to a sleeve 233 which extends a short distance intothe transmission housing where it carries a crank 33 having a ball endengaging in the bore of a bushing 23! carried by a bell-crank 238 whichis actuated thereby, the bell-crank being pivoted on a stud 239. Thisbell-crank, as will be seen, is adapted to slide the valve 203 tovarious positions, defined by a plurality of spring ball detent recesses243.

The valve 2 is shown in Figures 5 and 11 in the position at which thetransmission would automatically shift upwardly through its severalspeeds at the predetermined velocities. If, by means of the describedmanually controlled linkage the valve 204 is moved progressivelydownward to each of the different recesses, the transmission speeds willbe changed from fourth to third to second to flrst to neutral and thento reverse in the order stated. Whichever such detent position the valve204 is set back to, the transmission will automatically shift up to, butno higher. For example, if the valve be set back one detent position,the transmission will automatically shift up to third speed but not tofourth, while if it were running in fourth speed, movement of the valveback one such position would immediately change to third speed withoutrequiring any other action on the part of the operator.

Movement of the valve 233 requires no change in the automaticallyselected position of the valve transmission speeds cannot thereby bebrought 2,381,786. above the highest selected by the automatic valve,but can be lowered. however, applies only to manual'changing ofthespeeds through the forward range and neutral, but not reverse. If itis not desired to operate the transmission automatically through theautomatic system described, this valve alone is adapted to manuallyeflectuate the speed changes desired.

The .downward movements of the manual valve 204 to the several positionsmentioned are progressively shown in diagrammatic Figures 12 to 16inclusive. With the manual valve dropped one notch, to the "3rdposition, as shown in Figure 12, port 208Dis cut ofl,but since ports208D, 205B, 2 I F, and valve chambers mx, 200K, 2|0X are all equallyspaced, valve passage 2081! then serves to connect passages 206B, 206b,and

Positive maintenance of the transmission in neutral condition iseifected by moving the manual valve down one position further, to thepoint,

- indicated in Figure 15, where all of the transvalve passage 200xconnects passages 2|0F, 2 Mi.

It will be noted that although passage 209E is cut off by valve 204, thesupply to clutch E is maintained through a bridging slot 200 out in thevalve upon its edge which passes over the ports 2|9, 2|9e, 2| lc. Slot200 intersects slot 2|2, which provides communication with chamber 205through passage 98, and a connecting channel 94 which encircles a partof the sleeve surrounding valve 204. When the valve 204 is in 3rd"position, slot 200 connects passage 2l0 directly to the passage 209eleading to clutch E, while slot 2|2 and passages 94, 98 also provideconnection to the chamber 205. Valve channel 200K then also connectspassages 2| |C, 2||c, so that it is also still possible to engage clutchC, if the automatic valve is dropped to second speed position while themanual valve remains in third speed position. Pressure chamber-11 ofclutch D is also vented by a slot 95 formed in the side of valve 204near the top and serving to progressively connect passages 208d, 206b,2|0f, to atmosphere as the valve is moved downward. In the 3rd"position, disengagement of clutch D (used only in 4th) is efiected inthis manner, It will also be appreciated that with the manual valve inthe third speed position, automatic valve may be dropped to flrst speedposition, cutting ofi clutch F but maintaining engagement of clutches Cand E, as required for first speed operation.

Upon movement of the manual valve down still farther, to the secondspeed position shown in Figure 13, clutches D and B are both disengagedby venting of their pressure chambers through side slot 95 of valve 204,while energization of clutch Fis still possible by reason of the factthat valve passage 208)! then connects passages 2|0F, 2|0f. Clutches Eand C are then both supplied through slot 200 in valve 204, whichprovides connection between their feed passages 209e, 2| lo and thefluid pressure supply. The automatic valve 20| then functions in eitherfirst or second position, but is not efiective in higher positions, aswill be apparent.

Figure 14 shows the manual valve moved down another predetermineddistance, to the first speed position, designated 1st. Clutches B, D,and F are then all deenergized, by connection of their feed passages toatmosphere by slot 95 of the manual valve, since these clutches are notused in first speed. The feed to clutches C and E is mission clutchesare disengaged due to disconnection by the manual valve and ventingthrough the slots 05 and 200, which, as shown in the view in question,then connect all of the feed passages 208d, 200b, 2|0f, 200e, and 2l|ctoatmosphere. At this time the clutches are disconnected from the pressurefluid'supply from both pumps, and the feed from front pump 2|! is alsovented to atmosphere by slot 200.

When the manual valve 204 is in the neutral position, the pressure fromthe front pump being vented from its lower end, as stated, is exhaustedfrom passage 2|9 and cannot reach passage 220 and through it thepressure chamber 33. The main clutch is therefore disengaged, orprevented from engaging, and the driving connection from the engine isbroken.

Reverse Operation For reverse to become effective when the manual valve204 has been moved down to such position (shown in Figure 16), thevehicle must be travelling slowly enough so that the automatic valve MIis in the first speed (1st) position. The pressure fluid for operatingthe reverse cylinder 99, and the clutches B and C when in reverse, issupplied from chamber 205 through an outlet pasage 92 which connectstherewith at the extreme lower end, so that the pressure fluid can onlyreach it when the automatic valve is in its lowermost position. Passage92 terminates in a port 82 at the manual valve. Other ports at the samelevel form connections with connecting passages 84B, 850, which lead,respectively, to the feed passages 206b, 2| Ic. Another port, also atthe same level, leads to the passage 243 and connecting conduit 244,whichcommunicates with a fitting 244' in the cylinder 99 (Figure 8).When the manual valve is in the reverse position, the chamber 2|0Xtherein connects all of these ports, so that fluid from the front pumpis then delivered from chamber 205 through passage 92 and the ports inquestion to clutches B and C and to cylinderBS (whose functions willpresently be explained), as required for reverse operation. Smallclosing bridges ll, 12, are so carried by the manual valve, extendingacross the slots 95, 200, respectively, that when this Valve is in thereverse position they cover the feed passages 206b, 2|lc, and preventventing of the pressure chambers of clutches B and C, which may thus beenergized by pressure fluid delivered thereto through passages 84B, 850,as previously stated. Only clutches B and C being employed, inconjunction with main clutch A, for reverse operation, the othertransmission clutches are maintained in. the deenergized condition bythe manual valve when in the reverse position, but the fluid from thefront pump is then delivered to the chamber 205 through chamber 01 inthe manual valve.

Since the valve 20| is moved only by the pressure fluid from the rearpump 63, this valve will not be moved out of its low gear position whilethe vehicle is in reverse-as in such case the rear pump is'also runningbackwards and therefore supplying no fluid pressure. A further safe-,guard, which is effective when shifting back and forth through neutralto forward and reverse is also provided and will be described later. Y

It will be noted that in reverse operation clutches D and E aredeenergized. As previously stated, for reverse drive to becomeeffective, it is necessary to reverse the action of overrunning clutch III and to tree the sections of overrunning clutch I30 for independentrotation. Pressure cylinders I01 (Figure 9) control the action ofoverrunning clutch I30. These pressure cylinders are supplied with fluidconcurrently with clutches D and E and are subjected to pressure wheneither clutch is engaged, but to no pressure when both clutches D and Eare disengaged.

During reverse operation, therefore, cylinders I01 are deenergized andsprings 93 of the operating mechanism for overrunning clutch I30 (bestshown in Figures 9 and 10), then turn the ring I20 counterclockwise, asviewed in Figure 9. Ring I23 is rotatably mounted in the inner or camportion I22 of overrunning clutch I 30, and carries lugs I29 projectingfrom one face ror engagement by the stems of pistons I21 and is alsoslotted at 9i to receive springs I2I which normally act to urge the cageI23 toward wedged position, bearing against lugs I24 carried by a plateI20 attached to the cage. The housing I25 in which the cylinders areformed is keyed as at I26 to the cam I22, and floats on the shaft, beingconnected through appropriately positioned radial channels(undesignated) with the internal passages feeding clutches D and E, onecylinder being connected to the passage feeding clutch D, and the otherto the passage feeding clutch E. When either clutch is energized, thesprings 93 are compressed, and ring I28 is then turned to and held insuch a position, by pistons I21, that springs I2I are effective tooperatively urge the cage I23 toward the wedging position. When bothclutches D and E are deenergized, however, springs 93 move the ring I28counterclockwise sufficiently so that the ends of slots 9|, in whichsprings I2I are mounted, engage the lugs I24 and so move the cage to aninoperative position in which the rolls are freed, as by alignment withsuitable depression I06 in the cam. The overrunning clutch thusfunctions whenever either clutch D or E is engaged, but is completelyreleased and its parts rendered freely rotatable, in the mannerpreviously described as necessary for reverse operation, when thetransmission is in reverse and both clutches D and E disengaged.

In order to reverse the operation of overrunning clutch III as is alsonecessary for reverse operation, its cage IOI is attached to a plate I02having an integral arm I03 projecting therefrom and operable by thepiston 91 which is fitted in cylinder 99. Arm I03 extends into anopening (undesignated) in the piston rod 96 and between spring-pressedplungers I which serve to yieldably hold the cage in either position towhich it may be moved by the piston.

The rollers I08 cooperate with flattened surfaces of the cam I01, havinga wedging position at each end of such surfaces and being free when nearthe middle thereof. The rolls are yieldably urged toward one end of theflats by a. spring I04 when the fluid pressure is not applied to thepiston 91. The overrunning clutch then functions in the directionnecessary for forward drive. When pressure is exerted, however, it holdsthe piston rod and so the arm I03 in such position as to compress thespring I04 and yieldably maintain the rolls in the opposite positionnecessary for reverse operation.

The fluid inlet 244' of cylinder 99 is connected by the conduit 244 withreverse feed passage 243 (Figure 16). Whenever manually operable valve204 is shifted to reverse position, fluid is delivered to passage 244,provided the automatic valve 2" is in its lowest (first speed) position.as previouslydescribed. Piston I1 is then moved bythefluidpressuretoshifttheeageofthe overrunning clutch to the positionfor reverse operation.

Manual control of main clutch The lever 234 is fixed to a cross shaft245 which extends across the transmission through the hollow shaft 236,carrying within the transmission casing a lever 240 having a ball endengaging a suitable socket in a lever 240 to actuate the same. Lever 240is pivoted with lever 230 upon stud 239. The end of lever 240 engages ayoke 249 fixed to the upper end of the stem of valve 230 and alsoextending over the end of plunger 250, to actuate the valve and plungersimultaneously. It should be noted that while Figure 7 comprises asection of valve 230 on a transverse plane, the yoke or connector 249 isshown, together with stem 250, turned from their actual position, forclarity of illustration.

The automatic second speed lock-in for the main clutch must be renderedinoperative before such clutch can be controlled manually. This is oneof the functions of the valve 230. Upon the first slight depression ofthe pedal controlling movement of the lever 248, the latter is moveddown sufllciently to carry the valve 230 down to a point which cuts oilport 25I in the sleeve of the valve 230. Port 25I is that through whichpressure fluid is supplied to port 23I and hence to the valve I53(Figure 3). This pressure source being cut off, the main clutch cannotbe held in engagement by the supplementary holding means provided by thevalve I50, and the clutch may be manually controlled through the primaryfluid pressure source. Since the upper portion of valve 230 is reducedin diameter, port 25I is connected to atmosphere to vent pressurechamber I60 as soon as the upper end wall of the valve has moveddownwardly far enough.

Since the determination and maintenance of fluid pressure from the frontpump in piston chamber 33 is dependent upon the relief valve 2I3 ifcentrifugal effect has closed the port I55 of valve I46, means isprovided to reduce gradually the eflective tension of spring 2I6 whichtends to close the relief valve. This will be seen to conformably reducethe pressure in chamber 33 which provides the clutch engaging pressure.Such means comprises a smaller spring 252 arranged inside the valve 2,which is hollow. The plunger 250 abuts one end of the spring 252projecting slidably through the hole in the end of the relief valve. Asthe plunger 250 is depressed more and more by downward movement of thelever L43, the spring 252 opposes the tension of spring 2I6 withincreasingly greater effect until a point is reached where it completelyovercomes the latter and permits the pressure fluid to be freely ventedto atmosphere through the port 226, thus releasing the main clutch bycompletely relieving the operating pressure from passage 220 and chamber33.

The main clutch may be manually operated at various pressures orcompletely released at will at any time in this manner, provided theengine speed is suflicient so that the centrifugal control elementsmaintain an effective pressure. In other words, engagement of thisclutch is al- Neutral safety lock Since the valve 2 may by means of itsoperating plunger or lever be moved with very little effort on the partof the operator, it is deemed advisable (since the engine may be speededup to a point where the centrifugally controlled main clutch is'readyfor instant engagement) to provide some means to prevent the operatorfrom shifting into forward or reverse without flrst depressing andholding down the clutch control pedal to its fully releasedposition.Such safeguard is provided in the form of a spring pressed, plunger 253,the end of which becomes engaged in a hole 254 in the bellcrank 2,whenever the latter is moved to its neutral position. In order to againmove the bellcrank 248 out of neutral or through neutral to eitherforward or reverse, the spring plunger 253 must be withdrawn, by meansof a lever 255 actuated by the cross shaft 245, the end of which leverabuts a pin 256 extending from the side of the plunger 253. These partsare so arranged that the clutch controlling pedal must be fullydepressedto rotate shaft 245 suiliciently to move the plunger 253 clear of thehole 254.

Hill-holding means In the transmission as shown, the parts are also soarranged that merely by holding the clutch pedal fully depressed, andshaft 245 rocked to the clutch-released position, hillholding means isrendered effective to prevent the car from rolling backward when thetransmission is in a forward gear, and likewise to prevent the car fromrolling forward when the transmission is in reverse gear. Since theclutch operating pedal may be made to work against extremely lightpressure, this hill-holding means, although not automatic, may bemaintained in effect, even for relatively long periods of time, withoutfatigue. In my preferred arrangement the mere weight of the foot issufllcient to operate the pedal.

The means in question provides for maintaining engagement of clutch Fwhile the vehicle is stationary. To accomplish this, a port 251 in thevalve sleeve 264 (Figure 7) communicates with the pressure fluid chamber253 of valve 230, which receives the output from the front pump, aspreviously stated, in such manner that when the valve 230 is moved downto its bottom position, this port communicates with the recessed chamber225, which chamber at this time is also still in registry with the port258 leading to the passage 2 supplying the pressure fluid to clutch F.This will be seen to shunt pressure fluid from the front pump directlyto the pressure chamber of clutch F, to fully engage it. At this timethe port 228 is closed by the upper wall of the valve, to prevent escapeof fluid therethrough.

Since the main clutchcontrolling pedal must be fully depressed toreleased position to effect this condition, .it will be seen that nodriving torque is being applied to the transmission at such time,the'engine being disconnected, as it should be under such circumstances.With clutch F engaged in this manner, and the main clutch disengaged,the sun gear III is held stationary with respect to the transmissioncasing. If the transmission is then shifted to or is in any of theforward speeds, ring gear 9|) cannot turn in the opposite direction,because the outer race of overrunning clutch III will not turn in suchdirection, and the planet gears 80 cannot drive the sun gear forward.Similarly, if the shift is in reverse, the overrunning clutch III islocked in the other direction, and the ring gear 90 therefore cannotturnforward. In both of these instances, however, the vehicle can coastfreely in the direction in which the shift is set. Therefore if theclutch F is so engaged by depression of the main clutch control pedalwith the vehicle moving in either direction, no harm will be done and noeffect will he noticed, as the disengagement of the main clutch allowsthe other parts of the transmission to become stationary or revolve withthe shaft I00, irrespective of the stationary condition of the sun gear.

In neutral the hill-holding means is not effective because the pressurefrom the front pump is being vented as previously explained.

Dual pump system Because of the use of two separate pumps in the mannerdescribed, one operated by the engine and the other by the driven shaft,means must be provided to prevent losing the pressure from one pumpthrough the other, when one is not running. For this purpose each pumpis provided with a relief valve such as that shown at 213 (Figure 5).The conduit ports, as 2", of these valves are closed by the valveplungers whenever fluid isnot supplied to them under sumcient pressureby their respectiv pumps to overcome the springs.

The main outlet of rear pump 63 is connected by the conduit andpassageway 259 to the valve body 4| at the front of the transmissionadja cent the forward fluid pump 62, whereby the pressure fluid from therear pump is also delivered to chamber 205 of valve 20!. rangement, ifthe car were being towed 0r coasting without the engine running, andwith the front pump idle, the pressure fluid from the rear pump, unlessport 2|! were closed by the relief valve, would flow out through theport 2l5 and back through the front pump, where it would be vented toatmosphere through the fluid intake. With the port 2 I! closed by therelief valve, however, this cannot occur, and pressure from the rearpump is therefore maintained in the system.

Similarly, when the front pump 62 is operating and the rear pump 63 isidle, the pressure fluid entering the recessed chamber 205 would escapethrough the conduits and tube 259 and the rear pump 63 were it not forthe fact that the conduit 2-59 discharges at the rear pump relief valve(un-v shown) in the same manner as the passage 2|9 and the port 2|! atthe front valve. This provision is especially important in connectionwith the rear pump for the reason that this is always idle until thevehicle is actually under way, and also because the pressure of thefluid delivered by the, rear pump system varies in predetermined steps.The pressure of the fluid is not great enough to open the relief valveof the rear pump until it has attained a speed sufficient to produce agreater volume than can escape'through the auxiliary port H0, or untilthe speed of the governor is high enough to close the last escape porttherein.

Pressure fluid is also taken through a branch passageway (not shown)connected with conduit 259 at a point forward of the rear pump relief Byreason of this ar-

